The two-phase interface process has proved itself for many years in the preparation of polycarbonates. The process renders possible the preparation of thermoplastic polycarbonates for a number of fields of use, such as e.g. data carriers (CD, DVD), optical or medical uses.
Polycarbonates may in principle be prepared by the two-phase interface process or the melt process.
By the two-phase interface process, they may be prepared completely continuously, as is described e.g. in EP-A 1 249 463.
In continuous process variants by the interface process it has been found in particular that the polycarbonates prepared contain a small amount of nitrogen which has been incorporated into the polycarbonate.
However, the properties of the polycarbonate, in particular the properties which are important for use in the field of data carriers, are adversely influenced by this incorporated nitrogen.
Polycarbonates prepared by a discontinuous process are conventionally free from nitrogen, but continuous variants are frequently desired for cost reasons.
Polycarbonates prepared by the melt process are conventionally also free from nitrogen, but these materials have other disadvantages, such as e.g. a high content of monomers, monocarbonates, oligomers and branched structures.
There was therefore the object of providing a completely continuous two-phase interface process in which the content of incorporated, bonded nitrogen is between 20 and 3 ppm.
DE-A 42 27 372 and EP-A 1 249 463 of the Applicant, in which the apparatus arrangement of the process according to the invention is already described, are presently relevant art. However, no doctrine at all or only an indication that the nitrogen content is critical or of how this would be counteracted is to be found in the prior art.